For the hydrate sodium sulfate decahydrate, calculate the percent of water (by mass) in the hydrates

You are given the hydrate Na2SO4.10H2O. You are required to get the percentage of water in this chemical substance. The first thing to do is to get the molar mass of Na2SO4.10H2O and Na2SO4. The molar masses are 322.24 grams per mole and 142.04 grams per mole respectively. The formula in getting the percentage of water is  

%=[1-(grams of Na2SO4/grams of Na2SO4.10H2O)]*100.  

Substitute the molar masses of Na2SO4.10H2O and Na2SO4.  
%=[1-(142.04 grams of Na2SO4/322.24 grams of Na2SO4.10H2O)]*100.
% of water = 55.92%

Bis the